WO2002035191A9 - Procede et dispositif pour la correction d'hysteresis de valeurs mesurees pour des capteurs a extensometres - Google Patents

Procede et dispositif pour la correction d'hysteresis de valeurs mesurees pour des capteurs a extensometres

Info

Publication number
WO2002035191A9
WO2002035191A9 PCT/EP2001/012288 EP0112288W WO0235191A9 WO 2002035191 A9 WO2002035191 A9 WO 2002035191A9 EP 0112288 W EP0112288 W EP 0112288W WO 0235191 A9 WO0235191 A9 WO 0235191A9
Authority
WO
WIPO (PCT)
Prior art keywords
hysteresis
circuit
model
value
weighting
Prior art date
Application number
PCT/EP2001/012288
Other languages
German (de)
English (en)
Other versions
WO2002035191A1 (fr
Inventor
Hans Guenter Koenig
Original Assignee
Schenck Process Gmbh
Hans Guenter Koenig
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Schenck Process Gmbh, Hans Guenter Koenig filed Critical Schenck Process Gmbh
Priority to AU2002219058A priority Critical patent/AU2002219058A1/en
Priority to EP01988853A priority patent/EP1340057A2/fr
Priority to US10/415,299 priority patent/US6928853B2/en
Publication of WO2002035191A1 publication Critical patent/WO2002035191A1/fr
Publication of WO2002035191A9 publication Critical patent/WO2002035191A9/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2268—Arrangements for correcting or for compensating unwanted effects
    • G01L1/2275—Arrangements for correcting or for compensating unwanted effects for non linearity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
    • G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
    • G01G3/14—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of electrical resistance
    • G01G3/1414—Arrangements for correcting or for compensating for unwanted effects
    • G01G3/1416—Arrangements for correcting or for compensating for unwanted effects for non-linearity

Definitions

  • the invention relates to a method for hysteresis correction of measured values in transducers with strain gauges, which measure the strain due to the action of force on a deformation body, according to the preamble of claim 1, and a device for carrying out the method according to the preamble of claim 10.
  • measurement sensors with strain gauges When recording measured values, measurement sensors with strain gauges are often used, which generate an electrical measurement signal due to the action of a force on an elastic deformation body.
  • These transducers are mainly used in weighing systems and for measuring forces, moments or pressures.
  • Such transducers and in particular load cells usually have a hysteresis error, which can be recognized in practice by the fact that two different measured values are supplied for the same load, depending on whether the measurement is carried out with increasing or decreasing load.
  • the main cause of this ambiguous deviation from the characteristic curve is frequency-independent damping processes in the material of the deformation body in the case of strains in the elastic range or, in borderline cases, the beginning of plasticization.
  • external friction effects also occur on the force introduction or joining surfaces.
  • hysteresis errors In addition to other linearity errors, these hysteresis errors largely determine the accuracy of the measurement results. These hysteresis errors are often reduced in practice in load cells and load cells by compensating for them as much as possible by hysteresis effects when applying the transducer elements (DMS). For this purpose, the strain gauges (DMS) and corresponding adhesives are selected, which have the opposite hysteresis as possible and thus keep the total hysteresis error low. The hysteresis error that remains in this way is, however, still subject to series distribution and cannot be rewarded by reworking. So far, transducers with very low hysteresis sensors have only been produced by selection from the series.
  • a method for reducing the hysteresis error is also known from DE 20 40 987 B2, which mechanically couples two measuring elements with opposing hysteresis to one another in a sensor.
  • the hysteresis error can be reduced in this way, reworking after production is also no longer possible here, so that all manufacturing-related tolerances are fully included in the measurement result.
  • such a device increases the mechanical structure enormously by producing a complex measuring spring.
  • the invention has the advantage that this correction method can be used with all hysteresis-based pickup systems with strain gauges. All that is required is a one-time determination of the load characteristic or individual load values in ascending and descending form, which are sufficient to represent a hysteresis model, whereupon correction values can be derived from the model for each measured value subject to hysteresis.
  • the invention has the advantage that in order to form the respective hysteresis model for the special transducer or the special balance, only its load characteristic or only a few determining load values have to be determined or specified, which already takes place during a normal scale measurement for adjustment, without the entire load history must be known, so that no special previous determination of a large number of coefficients is necessary.
  • the invention has the additional advantage that the hysteresis correction can be carried out both for a single transducer and for a large number of interconnected transducers, such as, for example, an entire balance, since the entire hysteresis error occurs through a subsequent numerical signal processing. It is particularly advantageous that this is done in the simplest way because of the derivation of the model from the existence of elastic dipoles and therefore only requires very little computing effort. In a special embodiment of the invention, it is advantageous that an additional weighting function also makes it possible to adapt to an asymmetrical envelope of the hysteresis without the hysteresis model having to be changed.
  • FIG. 1 shows a block diagram of the invention
  • FIG. 2 a development of the density function as a function of the expansion
  • 3 the envelope of a hysteresis model
  • FIG. 4 a computing program of the hysteresis model.
  • Fig. 1 of the drawing the invention is illustrated with the aid of a block diagram which contains a pickup 1 with a preamplifier 2 which supplies a measurement signal x, the hysteresis error of which is caused by a model 3, a weighting function 4, a multiplier 5 and a summing circuit 6 is corrected.
  • the sensor 1 is designed as a load cell that contains an elastic deformation body, on which strain gauges (DMS) are applied. These emit an electrical signal that is proportional to the weight load of the load cell 1. Since this load cell 1 contains a deformation body made of an iron alloy, the load cell 1 emits a signal which is associated with a hysteresis error, the non-linear course of which forms a so-called envelope.
  • This weight signal x which is subject to hysteresis, is amplified in a subsequent preamplifier 2 and fed to a model computing circuit 3. Load values are entered in this model arithmetic circuit 3, which when the load cell 1 is loaded up to a maximum value and a complete relief be run through.
  • At least one intermediate value is required in the ascending branch and at least one intermediate value in the descending branch.
  • Such a scale measurement with several measured values usually takes place when the weighing cell 1 or a scale is adjusted, so that usually no special input of the necessary load values is necessary for this.
  • a load does not necessarily have to occur when the load cell 1 or the scale is used for the first time, since all previous hysteresis-generating measured values are overwritten by the measurement and can therefore be disregarded.
  • the hysteresis model of the model circuit 3 is based on the knowledge that the load history leading to the hysteresis develops according to the following steps.
  • a calculation model is used, which is derived from the geometric interpretation of a bending beam. It is assumed that elastic dipoles exist that orient themselves under the influence of an elastic strain field and, like the elementary magnets, align them in the direction of tension. In the case of the bending beam, the distribution (dipole density ⁇ ) should only be considered over the height of the spring or the expansion body z. In a first approximation, all other room components can be neglected.
  • the edge extension ⁇ r can also be measured and the greatest strains occur on the spring or on the deformation element in the elastic range.
  • the dipole density ⁇ of the oriented elementary hysteresis inside the body therefore results from the distortion gradient of the deformation body according to the following mathematical function:
  • n number of load steps.
  • Body edge a new point of discontinuity in ⁇ . This point can only migrate towards the neutral fiber (NF). Fronts between two points of discontinuity are immobile, only the line segment between the edge and the first point is shifted in parallel. Converging points cancel each other out. If the marginal expansion is sufficiently large, regardless of the sign, any older internal structure is overwritten by the new front B '. If two points of discontinuity are deleted, there is a kink in the characteristic branch. In the case of a weakly damped "swinging out", starting with the maximum amplitude in ⁇ r , the entire stored information is deleted.
  • the moment of failure of an individual fiber can be obtained by the density function ⁇ multiplied by the fiber distance z.
  • C hysteresis strength
  • an internal hysteresis moment M h or an internal hysteresis force F h is obtainable, which is determined by a.
  • Edge strain error ⁇ h is kept in balance.
  • the remaining hysteresis moment M h or hysteresis force F h resulting from the load history results from the following mathematical function:
  • the factor C is initially selected so that the relative model hysteresis becomes 100%.
  • the adaptation to the sensor hysteresis to be corrected can then be carried out additionally by a weighting function P (x) in a weighting circuit 4.
  • P (x) in a weighting circuit 4.
  • a correction or auxiliary value h can be calculated for each measured value x determined.
  • the hysteresis model essentially describes the linearity deviation from a straight line in the form of a drop of the enveloping loop. Such an envelope of the auxiliary value h over the measured value x, which is subject to hysteresis, is shown in FIG. 3 of the drawing.
  • This envelope 7 represents a symmetrical drop-shaped course, the values of which are calculated in the model circuit 3 according to the program in FIG. 4.
  • the hysteresis model is described in the programming language "FOTRAN" and entered into the model calculation circuit 3, which thus calculates the respective auxiliary value h for each measured value x. Since the envelope 7 according to the model circuit 3 is an envelope in an ideal drop shape according to FIG. 3 of the drawing describes, an adaptation to asymmetrical hysteresis curves that deviate from this drop shape 7.
  • a weighting function is also provided which describes a linear dependency P (x) by means of which the asymmetries of the hysteresis curves can also be taken into account in the weighting circuit 4 Since this weighting function P (X ) also contains an adapting factor C of the sensor hysteresis, the model computing circuit 3 can be used for all sensors with hysteresis.
  • the weighting function P (X ) as the form of the respective weighting factor w is multiplicatively linked to the respective auxiliary value h and fed to a summing circuit 6 as a correction factor.
  • This weighting factor w can ideally have the factor 1 for an ideal drop shape 7 of the envelope as described above or contain an adaptation of the measured hysteresis to the relative model hysteresis. Since this weighting function also includes a linear adaptation to a deviation of the ideal drop shape 7 of the hysteresis model can, the weighting function circuit 4 additionally calculates the respective deviation based on the measured value x which is subject to hysteresis. The resulting total weighting factor w multiplied by the auxiliary value h results in a correction value at the output of the multiplier 5 to take account of the respective hysteresis error.
  • the determined correction value is linked additively with the correct sign with the hysteresis measured value x, so that the measured value y adjusted for the hysteresis error is then available for further processing or display at the output of the summer ⁇ .
  • Such a correction method can be carried out by means of hardware or software computing circuits.
  • Such a correction method is suitable for both analog and digital sensor circuits or scales. In particular, it does not require any special adaptation to the special design of the sensors or scales, but can only be carried out by recording the rising and falling load characteristic curves.

Landscapes

  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Force Measurement Appropriate To Specific Purposes (AREA)
  • Measurement Of Force In General (AREA)

Abstract

L'invention concerne un procédé et un dispositif pour la correction d'hystérésis de valeurs mesurées d'un ou de plusieurs capteurs (1), déterminées au niveau d'un corps déformable pourvu d'extensomètres. Selon l'invention, chaque valeur mesurée x affectée d'hystérésis est corrigée de l'erreur d'hystérésis. A cet effet, on réalise, à partir d'une caractéristique de charge enregistrée et de la théorie de la densité dipolaire des hystérésis élémentaires orientées à l'intérieur du corps déformable, un modèle d'hystérésis à l'aide duquel on déduit, avec les valeurs mesurées x affectées d'hystérésis déterminées et au moyen de l'historique de charge enregistré, une valeur de correction qui sert à corriger l'erreur d'hystérésis.
PCT/EP2001/012288 2000-10-28 2001-10-24 Procede et dispositif pour la correction d'hysteresis de valeurs mesurees pour des capteurs a extensometres WO2002035191A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AU2002219058A AU2002219058A1 (en) 2000-10-28 2001-10-24 Method and device for the hysteresis correction of measured values for sensors with extensometers
EP01988853A EP1340057A2 (fr) 2000-10-28 2001-10-24 Procede et dispositif pour la correction d'hysteresis de valeurs mesurees pour des capteurs a extensometres
US10/415,299 US6928853B2 (en) 2000-10-28 2001-10-24 Method and device for the hysteresis correction of measured values for sensors with extensometers

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10053667A DE10053667A1 (de) 2000-10-28 2000-10-28 Verfahren und Vorrichtung zur Hysteresekorrektur von Meßwerten bei Aufnehmern mit Dehnungsmeßstreifen
DE10053667.0 2000-10-28

Publications (2)

Publication Number Publication Date
WO2002035191A1 WO2002035191A1 (fr) 2002-05-02
WO2002035191A9 true WO2002035191A9 (fr) 2002-09-19

Family

ID=7661496

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2001/012288 WO2002035191A1 (fr) 2000-10-28 2001-10-24 Procede et dispositif pour la correction d'hysteresis de valeurs mesurees pour des capteurs a extensometres

Country Status (5)

Country Link
US (1) US6928853B2 (fr)
EP (1) EP1340057A2 (fr)
AU (1) AU2002219058A1 (fr)
DE (1) DE10053667A1 (fr)
WO (1) WO2002035191A1 (fr)

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JP2004077293A (ja) * 2002-08-19 2004-03-11 Techno Link Co Ltd 重量測定装置
US7228247B1 (en) * 2005-11-09 2007-06-05 Siemens Vdo Automotive Corporation Sensor hysteresis reduction
DE102005055910B4 (de) * 2005-11-22 2010-04-22 Johnson Controls Automotive Electronics Gmbh Verfahren zur Fehlerkorrektur einer Einstellvorrichtung in einem Kraftfahrzeug und Einstellvorrichtung in einem Kraftfahrzeug
US7534970B2 (en) * 2006-06-15 2009-05-19 Schenck Accurate, Inc. Counterbalanced dispensing system
CN101858811B (zh) * 2010-06-18 2012-02-01 西安交通大学 高精度压力传感器信号补偿方法
CN112304412B (zh) * 2019-07-31 2022-05-31 梅特勒-托利多(常州)测量技术有限公司 称重装置的滞后补偿方法

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Also Published As

Publication number Publication date
AU2002219058A1 (en) 2002-05-06
US20040059532A1 (en) 2004-03-25
WO2002035191A1 (fr) 2002-05-02
EP1340057A2 (fr) 2003-09-03
US6928853B2 (en) 2005-08-16
DE10053667A1 (de) 2002-05-08

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